The long-term aim is a better understanding of the auditory processes that allow us to hear in background noise, and the effect of early hearing loss on those processes. Aim 1 will investigate the hypothesis that children require a greater level of temporal detail for speech identification than adults. The aim will also investigate the effect of sensori-neural hearing loss on the processing of speech in noise by hearing-impaired children. These studies will evaluate the hypothesis that hearing-impaired children may be at particular disadvantage because speech perception may be impeded not only by hearing loss factors, but also by factors related to limited speech/language experience. Aims 2 and 3 investigate monaural and binaural temporal resolution, respectively. Aim 2 will investigate the development of monaural temporal resolution in children. This work will test the hypothesis that children may exhibit a general developmental deficit in temporal processing due to inefficient weighting of stimulus information over time. Aim 3 investigates the possibility that binaural spectral resolution (the wide binaural critical band) can be acounted entirely in terms of the outputs of the left and right auditory filters centered on the signal frequency. A key hypothesis is that limitations on binaural temporal processing blunt binaural acuity as the noise bandwidth increases and interactions among increasingly widely spaced spectral components influence the stimulus envelope and the rate of change associated with binaural difference cues. A series of experiments is proposed that will allow us to test between this hypothesis and the currently popular hypothesis that the wide binarual critical band results from changes in the availability of across-channel cues with increases in masker bandwidth. Psychoacoustic studies will use standard, adaptive testing techniques, and speech will use a combination of adaptive and fixed block methods. All phases of the project will include age-matched control listeners. Data will be analyzed using analysis of variance and correlation procedures. There are two ways in which the proposed work relates to public health: 1) the data from the studies on hearing loss will provide information about the effect of early hearing loss on the development of speech perception;2) the studies on hearing abilities in normal-hearing children and adults will provide information about human abilities to hear signals in noise, the most common problem experienced by patients having hearing losses.This project is directly relevant to public health in that it investigates possible forms of hearing disability in children who have sensori-neural hearing loss. The project also investigates hearing processes that underlie the ability to hear signals in background noise. This is relevant to public health because poor hearing in background noise is the most common complaint of patients with sensori-neural hearing loss.